Electric resistance welding



"T. E. MURRAY ETAL ELECTRIC RESISTANCE WELDING July 2, 1946.

Filed Feb. 12, 1942 s Sheets-Sheet i IN KENTORS 47-7 RNEYY July 2, 1946. 'i'. E. MURRAY rz-rm.

4 ELECTRIC RESISTANCE WELDING Filed Feb. 12, 1942 S SheetS-Sheeb 2 INVEN 6 5'.

A77 ENEY Jul 2, 1946. T. E. M'URRAY ET AL 2,403,229

ELECTRIC RESISTANCE WELDING Filed Feb. 12, 1942 6 Sheets-Sheet s v .INV NTORS 36 v f BY f 147' OQNEY 'r. E; MURRAY ETAL ELECTRIC RESISTANCE WELDING July 2, 1946.

'Filed Feb; 12, 1942 s Sheets-Shqef. 4

' i l AT OIPNEY July 2, 1946.

1'. E. MURRAY ETAL ELECTRIC RES ISTANGE' WELDING Filed Feb. 12, 1942 6 Sheets-Sheet 5 &

, avg-gram A7 OE/YEY y 1946- '1'. E. MURRAY ETAL.

ELECTRIC RESISTANCE WELDING Filed Feb. 12} 1942 6 Sheets-Sheet 6 5 $2 8 3w r mm 1 2 32 handling of the welded article.

uNl'rEo; STATES PATENT oFFicE oi York Application February 12, 1942, Serial No. 430,524

r 1 The invention herein disclosed relates to electric resistance welding. and .comprehends a method and apparatus for effecting a weld and trimming the extruded burr.

In electric resistance or a flash welding of two pieces of metal, the pieces are heated, in the weld area, by the passage of a heavy electriccurrent therethrough. When the pieces are heated to a point where the metal in the weld area becomes plastic, the pieces are moved together beyond the contact plane to cause the metal of each piece to flow into and become ingrained in metal of the other piece. The excess metal is extruded laterally in the form of a burr. This burr, except perhaps in some special cases, must be removed irom the article that is formed by the welding of the pieces. When the metal of the burr is cold, it is tough, and the removal of the burr often presents a dimcult machining operation.

By this invention there is provided a method,

' and a machine for carrying out the method, by which the burr extruded at the joint is readily and quickly removed with a minimum amount of In accordance with the method of; the invention; the burr is trimmed or removed while the metal is hot from the welding heat. The pieces of metal to be joined are placed between electrodes and a heavy current is caused to flow through the pieces in the area of the weld. When the metal becomes plastic; the pieces are forced together under heavy pressure and the welding current is cut off. .Im--

mediately thereaiter and while the extruded burr is still hot from the welding heat, the blur is trimmed.-

Preferably, though not necessarily, the burr 'is trimmed while the welded pieces remain between the electrodes. Also, it is advantageous to effect the trimming of the burr mechanically and in coordination with the action of the welding operation. To this end, there is provided, by this invention, a machine which eife'cts the weld and trims the burr immediately upon the completion of the welding operation and while the burr is hot from the welding heat.

One specific embodiment of the machine forming a part of the invention is disclosed in the accompanying drawings. This machine together with its operation in performing the steps of one embodiment of the method of this invention is described in detail below. From this description cured to an extension 9 on the base i. cylinder 8, there is a, piston 10 to which there is a clearer understanding of the invention may be had.

The drawings include:

40mm. (Cl. 29-43) Fig. 1 which is a side elevation of a machine,

, party of the. machine being. .illustrated somewhat diagrammatically.

Fig. 2 which is a plan of the portion of the machine.

Fig. 3 which is an end elevation oithe trimmer.

Fig.4 which is a section taken along the line l-Jof Fig. 2. a

Fig. 5 which is a transverse, sectional elevation taken along line 5-5 of Fig. 1.

Fig.6 which is a side elevation of a cutting tool.

Fig. 7 which is a transverse section taken at. I

1-4 of Fig. 6.

Fig. 8 which is a plan or the cutting tool: and Fig. 9 which is a diagrammatic representation oi the control for the mechanism.

In general, the machine illustrated in the drawings includes mechanism which efiects the weld and trims the burr'while the burr is still hot from the welding heat. Part of the mechanism for eilecting the weld is illustrated at the left of Fig. 1. This mechanism, which is illustrated somewhat diagrammatically may be in general similar to welding machines of this kind that have heretofore been used and that are well known in the ,art. .Preferably, however the welder may take the form of that which is disclosed in the copending application of George J. Frischmann et al., filed January 22, 1942, Serial- No. 427,730.

The welder illustrated in the drawings includes a a base or frame I on which there is secureda bed plate 2 that carries an electrode shoe 3. Se-

cured in the electrode shoe, there is an electrode l. Cooperating with the electrode l there is a movable electrode 5, that is secured in an electrode shoe 8. Th electrode shoe 6 is in'tum secured to a mova le ram plate I, mounted for vertical movement toward and away from the electrode 4.

The ram plate 1 is mountedin guides (not shown) and may .be moved from the position shown to a position spaced from the electrode 4. For the purpose of moving the ram plate I, there is provided a hydraulic cylinder 8 which is se- Within secured a piston rod Ii. The end of the piston rod is provided with a flange II that is secure to the ram plate 1. Suitable hydraulic connections are made to the cylinder on opposite sides of the pistons to effect movement of the piston in the cylinder. The ram plate fl carries a control rod 13 upon which there is mounted a control cam l4.

- The ca'm 'i4 servesrto actuatetheleveriiof a e. limit switch It that is secured'on the base explaced together with the section I 8 within the electrode ,4, the electrode 5 being raised and spaced from the electrode 4. The electrode 5 is then brought down to engage the section I! and eifect a pressure contact between the edges of the sections [1 and I8. Inthis position, the electrodes 4 and 5 are in circuit so that current flows through the sections l1 and 18 in the weld area, i. e. the area between the electrodes. In this way side of-the article this burr the: tool continues to rotate in the same direction leads the tool and if the severed burr would be between the tool and the burr on the opposite side. v The mechanism for operating the cutting tool is illustrated in Figs. 1 to 5. This mechanism includes a base 23 upon which a frame 24 is mounted. On the base 23 there is mounted an electric motor 24, the pulley 25 of which is connected by a belt 26 to a pulley 21 secured to a shaft 28 mounted in hearings on the sides of the base 23. Within the base a train of reduction.

gears including gears 29, 30 and 3! effect a driving connection between the shaft 28 and a gear 32 rotatably mounted on a shaft 33. The gear s2 is coupled to the shaft 33 through a clutch -34. In the particular machine'illustrated, the

thepieces 'are heated in the weld area until the metal becomes plastic and will 'flow. Uponslight' movement of the electrode 5, additional pressure is applied to cause the metal of each piece to nected by a link 36 to a cross head 31, the cross flow into and become ingrained in the metal of the other piece. As the addedpressure-is ap- .plied and the electrode i'moves toward the electrode 4 to effect the fusion of the metal of the sections, the cam 14 acts upon lever l5 to actuate the limit switch l6for a purpose that will hereinafter appear. Suitable limit blocks are ,provided between the electrodes 4 and S'to limit the amount of the take up as the weld is efiected. In the take up as the weld is effected metal is extruded at the joint-and forms a burr. In the welding of hollow articles, such as that disclosed,

. part of the metal is extruded inwardly forming 4 an inwardly extending burr.

The trimming mechanism disclosedis for the purpose of removing the burr extending inwardly in an'article such as that which is formed by the welding of sections l1 and 18. It will be observed that in such an article the opening there to indicated at I 9, is of a lesser diameter than the body of the article. For the trimming of the internal burr on such an article a particular trimming tool is utilized. A suitable tool for this purpose is shown in Figs. 6 to 8 inclusive.

The tool illustrated consists of a shank, shaped as illustrated, under-cut at 2|, and the tool proper. The tool includes a cutter 22. This cutter is of the general shape of the interior of the hollow article that is formed by the welding of the sections l1 and I8. It extends longitudinally,

'but, as illustrated in Fig. 8, in a smooth curve clutch 34 is of the kind known as a one rotation clutch. Such clutches are well known in the art and thisparticular clutch is not, therefore, illustrated in detail. On the end of the shaft 33. there is mounted a crank 35 which is provided with a counterweight 36. The crank 35 is conhead 31 being slidably mounted in a guide 38 secured to-the side of the base 33. Also connecting to the cross head there is a rack 38 which engages a pinion 38 that is splined on the reduced end. of a shaft 4|.

The shaft 4| extends longitudinally of the frame 24. At its reduced end the shatt 4| is journaled in bearings 42 and 43 which have a side of the cutter in the tool illustrated, forms a 7 cutting edge. In view of the fact that the opening IQ of the welded article is of lesser diameter than the body of the article and that the radius of the cutter is, in part, greater than the radius of the opening l9.-the toolmust enter the article with its axis out of line with the axis of the article. When entered in the article, the tool must be shifted so as to be substantially coaxial with the article. in which position the cutter en-- gages the interior surface of the article. The tool is then rotated first in one direction to trim the -certain amount of play so that the shaft 4l may be tilted at slight angle to the horizontal. The

shaft is alsorotatably mounted in a square bearing block 42'. The end of the shaft is provided with a tool seat 43' which receives the shank 20 of the tool. The shank of the tool and the tool seat in the shaft are provided with complementary keys and keyways that serve to prevent the shaft from rotating with respect to the tool. Also set screws 44 are provided for securing the tool in the shaft against relative longitudinal moveextension 46 and the bracket 48. These gibs serve to slidably mount the head on the frame. The

carriage includes a rectangular box-like section '54 in which the square bearing block 42 is received. The section 54 is provided with a cover plate 55 which is secured thereto by screws 56. There are two set screws 61 and 58 extending through the cover which serve to limit move-'- ment of the bearing block 42 in a direction towards the cover. The bearing block has secured thereto on each side thereof wedge-shaped cams 58' and-60 which cooperate with wedge-shaped cams 6| and 62 secured to the carriage and positioned to engage the cams 56 and 60 upon forward longitudinal movement of the carriage with respect to the square bearing.

Behind the square bearing 42, there is mounted on the shaft 4! a thrust plate 63. Against-this burr on one side and then in the other direction the reason thatwhen one burr is cut from one thrust plate there is a steel collar 64 that is shrunk on the shaft. Surrounding thesteel collar 64 there is a bronze retainer 65 which is secured to the square bearing by bolts. The bronze retainer 65 is provided with an extension 66 through which aset screw extends. The limit l screw 91 is positionto engage the edgeof the i u. Also actuated by the solenoid through the cover it upon. relative rearward movement of the Preferably, the piston is acted carriage with respect to the square bearing.

The carriage 45 is provided with an extension 98 to which the'end of a piston rod 69 is secured. This piston rod 69 extends from a piston that is slidably mounted in a cylinder II. The cylinder Ii is secured to brackets 12 onthe frame 24.

pressure. a

InFigsJ andzthe' shaft4l isshowninthe operativeposition, i. e. the forward position; the

inoperative position is that in which the carriage upon by air under plunger 83, there is a control rod 85 which carries a cam 86. The cam 89 is mounted on the I control rod in position to actuate a lever- 81 of a switch 89 that is mounted upon the base. Another switch 89 mounted upon the base is actuated, upon the rotation of the shaft 93 by a cam 99 that is secure to the section of the clutch which is secured to and rotates with the shaft 33.

The controls, and their interconnection, for the machine above described are illustrated diametri- Cally in Fig. 9. In Fig. 9 there is illustrated a source of electric current'consisting of the line 46 is drawn to the right from the position shown in Figs. 1 and 2. When 'a weld is eiiected, in the manner hereinafter disclosed, air is admitted to the head end .of the cylinder Ii, behind the piston l0, and moves the carriage 49 to the left, to the position shown in Figs. 1 and 2. The square bearing and the shaft 4i are moved with g [the carriage until.a-collar;l3,.mounted-.on theextended reduced end of shaft 4|, engages the end of the adjacent bearing. Further forward movement of the shaft 4! and-the bearing block are thus restrained. The carriage, however,

I .moves further and in doing so, the cams 9i and 92 engage the cams i9 and 60 and raise the square bearing in the carriage until it engages the limit screws 51 and 59. Thus the tool is entered in the article between the electrodes axially out of line with the axis of the article, and when inserted it is raised to substantial axial aline- "ment. When the tool is enteredinto the articleoccur directly.

wires 9! and 92 and the neutral 93.

' Upon actuation of limit switch I 6, two things The welding current is cut oil: and the normally open circuit to the trimming mechanism controls is closed. In circuit with the normally open switch I6 isthe coil of .a relay 95. This relay includes normally closed or bridged contacts 95 and 95b-which are in circuit 7 with the primary of the transformer- 99, the secondary of which is connected, during the welding operation, to the electrodes 4 and 5. The circuit to the coil 95 includes linewire 92,'switch It, a wire 95-4, coil 95, a wire 95-2 and line wire 93. Upon actuation of the relay 95-, the connection between contacts 95a and 95b is broken thus opening the circuit to the primary of the transformer,

cation of the rack 38 the shaft 4| is caused to- 3 rotate a partial revolution in one direction, then in the opposite direction and returned to the original position. While the mechanism disclosed utilizes a one rotation clutch, it may be de-' sirable, in some instances, to utilize a clutch that makes two or more revolutions before disengaging. Several movements of the cutter across the'joint may. in some instances, leave a smoother surface at the joint.

The shaft :3 overrides, slightly. the one revolution. The rack and cross head, however, overbalance the counterweight and tend to move to the lowermost position. Such action is prevented and the shaft 39 positioned as desired by a lever 11 that is pivotally mounted on the frame as at 19. A spring I9 acts to urge the lever 11' towards the counterweight 96. The lever is provided with a hook-shaped end 99 which engages the edge of the counterweight 96. In operation the shaft 31 rotates in the direction of the arrow 9i. As it passes the hook-shaped end of the lever II, the

lever falls in the place so that upon reverse movement under the weight of the rack and cross head the lever engages the counterweight and positions the shaft 4| in the proper position for removing the tool. Air is then admitted to the piston rod end of the cylinderand the hea end is connected to atmosphere. The carriage moves away from the electrodes. In its initial movement the square bearing 42, shaft 4| and the tool are lowered and then the tool is withdrawn.

The clutch is actuated through a solenoid 82, the plunger 99 cfwhich act upon a'clutch lever scribed it bridges contacts 95d and 950.

which circuit includes line wire 92, a wire 96-l,

" transformer primary, a wire 96-2. a switch 91,

a wire 96-4, contacts 95a and 95b, a wire 96-4 and line wire 9|. The switch 91 may be either a circuit breaken'a manually operated or magnetically operated switch to suit an particular condition; it is, however, closed during the welding operation. This circuit is preferably tied in with the circuit of the aforesaid application Ser.

No. 427,730, filed January 22, 1942, so-that as here,

the' welding current must be cut off before the circuit to the trimming mechanism controls are completed.

When the relay 95 is energized as above de- This action. connects the line wire 92 to a wire 92-3. The connection is effected through the switch [8,

*wire 95-l, a wire 92--i contacts 950 and 95d, and

a wire 92-2. In this manner the welding current is cut oil and the line wires connected through-to the trimmer controls, the neutral 93, line 9| and a branch of 92 (hereinafter described) being connected through a three pole manually operated switch I90.

The first action is to efiect, through the control of the pneumatically operated piston, the forward movement of-the tool. This action is controlled by a valve "II. The valve is of a kind well known in the art and it is normally positioned by a spring to connect the head end of the cylinder to exhaust and the opposite end to air under pressure. The valve is magnetically actuated to reverse theseconnections, that. is, when energized the valve is actuated to connect the head end of the cylinder to air under pressure and the opposite end to exhaust or atmos- "Rd. The coil l02e of therelay Ii is energized directly upon operation of relay 95. .The circuit to the relay includes line 92, switch it, relay contacts 950 and d, line connected wire 92-4,

' contacts I8 3a I886 bf shaman; closed'time relay I8.8,'a wire I82-I, coil I82e and awire I82-2 to a line-connected wire 83-I connected to the neutral line 83.

When the relay closes contacts mm and I821) are bridged also contacts I82c and I82d are bridged. The circuit to' the valve I8I includes the contacts M241 and NH), this circuit includes the line connected wire 82-3, a wire I8 I-I, contacts I82a and I82b, a wire I8I-2, air valve- IN and line connected wire 8I-I. Thus on the bridging of the contacts I 82a and I82b,the air. valve solenoid is connected across the line wires the piston, a cam operated switch closes a circuit to a signal light I85, this circuit remains closed and the signal lightlighted until the piston returnsto its initial position. Thecircuit for this signal'light includes line wire 8i, a wire I85-I, switch I84, a wire, I85-2, light I85 vand a wire I85-3 which is connected betweenone-side' of the light and line-connected wire 83-I.

As explained above when the carriage or head is moved to its foremost position, the limit switch I6 is actuated. Upon actuation, a circuit is closed to the clutch solenoid 82. This circuit includes line-connected wire 83-I, a wire 82-I, switch 18, a wire 82-2, solenoid 82, a wire 82-3, contacts WM and I88b of a relay I88, which contacts are normally bridged, and a wire 82-4 connected to a line-connected wire 82-5. Thus, the solenoid 82 is connected across theline wires 83 and82.

With. the energization of the solenoid 82, and the attendent operation of the clutch lever, the switch 88 is actuated. The switch 881s a single pole double throw switch. With the solenoid 82' de-energized, this switch connects contacts 880 .in circuit is completed through the the relay, this hold in circuit includes line-cone I When the relay I86 'is'energized, as previous stated, the contacts I880 and lid are connected. By the connected contacts I880 and I88d a holdnected wire 82-2 9. wire I86-3 contacts I880 and I85d, a wire I86-4, relay coil I86, wire 82-4,

wire 82-5 and line-connected wire 82-3. Also by the bridging of circuit is completed to the solenoid of the time delay relay I83, this circuit includes wire HIE-3, wire HIE-4, a wire I83-I, solenoid of relay I83, a wire I83-2, contacts 88a and 88b to line-connected wire 82-5.

This time delay relay is set for a time which is in excess of the time for the complete cycle of operation of the trimming mechanism. As the switch 88 is, upon the release or the clutch lever by the de-energizing of the solenoid 82, now in position to connect contacts 88a-and 8811, the circuit of the relay I82 again includes the normally closed contactsof the time delay relay. When the period of time for which the time delay relay is set passes, the time delay relay is actuated and the circuit to the relay I82 isbroken. When this circuit is broken, the solenoid of the air valve MI is de-energized and the valve is actuated by the spring acting thereon to connect the head end of the cylinder to atmosphere and and 88b. When the clutch solenoid is energized and switch 88 is actuated, it connects contacts 88a with 880, by-passes the contacts of the time delay relay I83 and opens the circuit of the time delay relay. When the contacts 88a and 880 are connected together, .the line-connected wire 82-5 which is connected to. the contact 88a is then connected to a wire I82-3 which is directly connected to thewire I82-I. Thus the energization of. the relay I82 becomes, upon the actuation of the switch 88, independent of the time delay relay I83.

As the shaft 38 rotates, the cam 88 thereon is ment of the shaft 33, to actuate the switch 88. Actuation of the switch 89, which is a normally opened switch, closes the switch to connect the contacts 884: and 88b thereof. This action closes a circuit to relay I88. The circuit to relay I88 includes the line-connected wire 82-5, wire 82-4, contact I86a to which one side the coil I88 is connected, wire I88-I contacts 88a and 88b of switch 88, and a 'wire I88-2 connected to wire 82-2 which is connected through the switch I8 and wire 82-I, to the line-connected wire 88-I. In this manner, upon actuation of the switch 89, the relay I86 is operated to open the contactsl88a and I86!) and to close contacts I88c and brought to a position, after predetermined movetrimmed while the engaged thereafter until it is automatically dis- 4 engaged upon the completion oi one revolution of the shaft 33.

. switch I8, therelay the piston-rod end to air under pressure. The piston is thus moved rearwardly in the cylinder. As the piston starts to move the switch I6 is open and when it reaches the final rearward position the switch I84 is open, Thus, the shaft 33 has made one complete revolution and has come to rest when the time delay relay functions to withdraw the tool, Upon the opening of the I88 is, of course,'deenergized and all-of the relays and contacts re-established in their initial relation.

From the foregoing description of the mechanism disclosed in the drawings, it will be seen that by the starting of the mechanism the weld.

purpose.

From the foregoing description of the method as related to welding the particular pieces illustrated and trimming the burrs on the welded out. the method, it will be apparent to those skilled in the may be welded what amounts handling of the article.'

' It will be obvious that various changes may be made, by those skilled in the art, in the details of the steps of the method and the specific'mechthe contacts I860 and NM asolenoid of similar mechanism arranged for that particular piece, and of the mechanism suitable for carrying art that by this invention pieces and the extruded burr trimmed in to a single operation. The burr is 5 pieces remain in the electrodes and while the condition of the metal of the burr f is most favorable forthe trimming operation. This minimizes the eflort necessary for the trimming of the burr and minimizes the necessary anism disclosed in the drawings and described 3 above within the principle and scope of the in- 5 vention as expressed in the appended-claims.

holder towards the electrodes; means for-moving the tool holder transversely of said movement towards the electrodes, and means for efiectingtanular movement of the tool holder.

2. In the process of electric resistance welding of two pieces of metal, the steps including engag ingthe pieces between electrodes, heating the pieces in the weld area by the passage of an electric current therethrough, forcibly moving the electrodes under pressure to cause the'pieces to move together beyond theplane of contact thereof, cutting ofi the welding current and retaining the pressure on the electrodes and shearing the extruded burr while the piece is between the electrodes and the pressureis retained on the 10 trodes, heating the pieces in the weld area by the passage or an electric current therethrough, torcibly moving the electrodes "under pressure to cause the pieces to move together beyond the plane ofcontact thereof, cutting oi! the welding current and retaining the pressure on the electrodes to clamp the welded piece, and inserting a tool within the welded piece clamped between the electrodes and shearing the internal burr while the metal is still hot from the welding heat.

-4. In a machinefor effecting a weld by electric resistance welding, the combination comprising meansfor effecting a weld including elec-.

trodes for engaging the pieces to bewelded,

meansfor removing the burr extruded during the weld and control means therefor for eflecting operation thereof immediately upon completion of the weld, said burr removing means in-' cluding a cutting tool, a movably mounted tool holder, means for moving the tool holder towards theelectrodes; means for moving the tool holder transversely of said movement towards the elec- Ytrodes, and means for reflecting angular moveelectrodes and while the burr is still hot from the welding heat.

3. In the process of forming a hollow articleby electric "resistance weldingv the steps including engaging sectors of a hollow article between elecment of the tool holder.

THOMAS E, MURRAY. GEORGE H, PHELPS. GEORGE FRISCHMANN. 

